Masaya Hayami sports spiky silver hair, narrow brown eyes, and a prominent facial scar – a permanent mark from a rock thrown by Kirishima during high school. Hayami deliberately provoked the attack to test Kirishima's feared "Demon" reputation. He typically dresses in formal attire: a brick red button-up shirt, white blazer, matching slacks, a gold pendant necklace, and brown shoes. His personality is abrasive, aggressive, arrogant, foul-mouthed, and extremely irritable. A blood knight, he constantly seeks physical confrontations, especially with Kirishima, and possesses a hair-trigger temper. Personality assessments suggest either ISTP or ESTP types alongside an Enneagram Type 8w9, highlighting his pragmatism, adaptability, and competitiveness. Hayami's defining background is his deep-seated rivalry with Kirishima. After a decisive loss to Kirishima in their youth, Hayami became fixated on defeating him, viewing Kirishima as his ultimate target. This obsession drove him to wander and instigate random fights. Yakuza member Youji Kakihara recruited him by promising a path to reunite with Kirishima through the Kakihara family. Violent incidents linked to his pursuit of Kirishima later resulted in prison time. Upon release, Hayami discovered Kirishima had become a caretaker for Yaeka Sakuragi. He reacted with disbelief and profound disappointment, confronting Kirishima directly. Kirishima's initial failure to recognize him deepened Hayami's frustration. Rei Hojo intervened, mistakenly recalling their school dynamic as a close friendship, which further agitated Hayami. Unexpected dimensions emerged when Hayami was tricked into babysitting Ren Ninomiya, a mob boss's son. He revealed a competitive yet childish side, engaging Ren in board games. Hayami displayed poor sportsmanship and threw tantrums upon losing, illustrating manchild tendencies. This reluctant experience contributed to a subtle shift in his interactions, moving beyond his singular rivalry focus. Throughout his arc, Hayami adamantly proclaims himself Kirishima's rival, though Kirishima largely views him as an unknown rival. The facial scar remains a constant physical reminder of their history. His journey reflects the tension between his aggressive instincts and emerging relational experiences, particularly through forced caretaking responsibilities.